Disclosed herein are colorant compounds. More specifically, disclosed herein are colorant compounds particularly suitable for use in hot melt or phase change inks.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. Nos. 4,889,560, 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labelling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. Nos. 3,653,932, 4,390,369, 4,484,948, 4,684,956, 4,851,045, 4,889,560, 5,006,170, 5,151,120, 5,372,852, 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
While known compositions and processes are suitable for their intended purposes, a need remains for new yellow colorant compositions. In addition, a need remains for yellow colorant compositions particularly suitable for use in phase change inks. Further, a need remains for yellow colorants with desirable thermal stability. Additionally, a need remains for yellow colorants that exhibit minimal undesirable discoloration when exposed to elevated temperatures. There is also a need for yellow colorants that exhibit a desirable brilliance. In addition, there is a need for yellow colorants that exhibit a desirable hue. Further, there is a need for yellow colorants that are of desirable chroma. Additionally, there is a need for yellow colorants that have desirably high lightfastness characteristics. A need also remains for yellow colorants that have a desirably pleasing color. In addition, a need remains for yellow colorants that exhibit desirable solubility characteristics in phase change ink carrier compositions. Further, a need remains for yellow colorants that enable phase change inks to be jetted at temperatures of over 135° C. while maintaining thermal stability. Additionally, a need remains for yellow colorants that enable phase change inks that generate images with low pile height. There is also a need for yellow colorants that enable phase change inks that generate images that approach lithographic thin image quality. In addition, there is a need for yellow colorants that exhibit oxidative stability. Further, there is a need for yellow colorants that do not precipitate from phase change ink carriers. Additionally, there is a need for yellow colorants that do not, when included in phase change inks, diffuse into adjacently printed inks of different colors. A need also remains for yellow colorants that do not leach from media such as phase change ink carriers into tape adhesives, paper, or the like. In addition, a need remains for yellow colorants that, when incorporated into phase change inks, do not lead to clogging of a phase change ink jet printhead. Further, there is a need for yellow colorants that enable phase change inks that generate images with sharp edges that remain sharp over time. Additionally, there is a need for yellow colorants that enable phase change inks that generate images which retain their high image quality in warm climates. Further, there is a need for yellow colorants that enable phase change inks that generate images of desirably high optical density. Additionally, there is a need for yellow_colorants that, because of their good solubility in phase change ink carriers, enable the generation of images of low pile height without the loss of desirably high optical density. A need also remains for yellow colorants that enable the use of substantially reduced amounts of colorant in, for example, an ink without decreasing the color and the spectral properties (L*a*b*) of the ink or jeopardizing the optical density or color of the prints generated with the ink. In addition, a need remains for yellow colorants that enable cost-effective inks.